S4C charging

[dmgroom]

Can someone explain why the engine has to reach 2200 RPM before the charging circuit kicks in on an S4C?

[Podie]

My S3c is the same... I assume it's a case of "they all do that sir!"

[PetrolTed]

Is that another S4 owner I see!? Hen's teeth etc...

[S3 Kieran]

I was told by my vendor that it was more of a 'check light' and only stays on until you rev past 2000rpm for the first time. Obviously, if your light comes back every time at idle, I guess you do have a problem!

Check you voltmeter reading whilst idling - hopefully will give more comfort?

[Rozza!!!]

It says a little bit about this in the 'bible'. IIRC the S2, S3 and S4 need 2200 ish revs, and the S1 and V8S need about 1200 or something like that.

Roy.

[GreenV8S]

In crude terms, the alternator uses an electromagnet and a moving coil to generate a voltage. Once the alternator is charging, it powers the electromagnet itself, but for the initial startup it depends on a small current supplied through the no-charge warning light, and residual magnetism in the magnet. Both these effects are quite weak and you need to spin the alternator up fairly fast before it will generate enough to kick itself into life. The engine RPM needed to spin the alternator up to this speed depends on pulley gearing, hence the alternator might be fine in a standard car but a bit lethargic in a TVR. Once it's been energised the alternator will keep charging down to very low rpm though (mine starts to drop out at about 600 rpm).

Hope this makes sense,
Peter Humphries (and a green V8S)